A solar cell includes a semiconductor substrate, a doping layer, a quantum well layer, a first passivation layer, a second passivation layer, a first electrode and a second electrode. The semiconductor substrate has a front surface and a back surface, and the front surface of the semiconductor substrate includes nano-rods. The doping layer covers the surface of the nano-rods. The electrode layers cover the doping layer. The quantum well layer having at least one first doping region and at least one second doping region is disposed on the semiconductor substrate. The quantum well layer includes polycrystalline silicon germanium (Si1-xGex). The first passivation layer and the second passivation layer cover the first and the second doping regions of the quantum well layer, respectively. The first electrode and the second electrode are electrically connected to the first doping region and the second doping region of the quantum well layer, respectively.